Lamina cribrosa pore shape and size as predictors of neural tissue mechanical insult

TitleLamina cribrosa pore shape and size as predictors of neural tissue mechanical insult
Publication TypeJournal Article
Year of Publication2017
AuthorsVoorhees, A., N. Jan, M. Austin, J. Flanagan, J. Sivak, R. Bilonick, and I. Sigal
JournalInvestigative Ophthalmology and Visual Science
Volume58
Pagination5336-5346
Keywordsanimal, Animals, Article, Biomechanics, compressive strength, computer simulation, connective tissue, Convexity, finite element analysis, Finite element modeling, Glaucoma, histology, intraocular pressure, Lamina cribrosa, Mechanical, mechanical stress, Microstructure, nervous tissue, optic disk, optic nerve, Optic nerve head, pathology, pathophysiology, physiology, polarization microscopy, pore shape, pore size, priority journal, shear strength, shear stress, sheep, Stress, tensile strength, tissue injury, tissues, visual system parameters
Abstract

PURPOSE. The purpose of this study was to determine how the architecture of the lamina cribrosa (LC) microstructure, including the shape and size of the lamina pores, influences the IOP-induced deformation of the neural tissues within the LC pores using computational modeling. METHODS. We built seven specimen-specific finite element models of LC microstructure with distinct nonlinear anisotropic properties for LC beams and neural tissues based on histological sections from three sheep eyes. Changes in shape (aspect ratio and convexity) and size (area and perimeter length) due to IOP-induced hoop stress were calculated for 128 LC pores. Multivariate linear regression was used to determine if pore shape and size were correlated with the strain in the pores. We also compared the microstructure models to a homogenized model built following previous approaches. RESULTS. The LC microstructure resulted in focal tensile, compressive, and shear strains in the neural tissues of the LC that were not predicted by homogenized models. IOP-induced hoop stress caused pores to become larger and more convex; however, pore aspect ratio did not change consistently. Peak tensile strains within the pores were well predicted by a linear regression model considering the initial convexity (negative correlation, P < 0.001), aspect ratio (positive correlation, P < 0.01), and area (negative correlation, P < 0.01). Significant correlations were also found when considering the deformed shape and size of the LC pores. CONCLUSIONS. The deformation of the LC neural tissues was largely dependent on the collagenous LC beams. Simple measures of LC pore shape and area provided good estimates of neural tissue biomechanical insult. © 2017 The Authors.

DOI10.1167/iovs.17-22015